Transcriptome analysis reveals steroid hormones biosynthesis pathway involved in abdominal fat deposition in broilers

Excessive abdominal fat deposition reduces the feed efficiency and increase the cost of production in broilers.Therefore,it is an important task for poultry breeders to breed broilers with low abdominal fat.Abdominal fat deposition is a highly complex biological process,and its molecular basis remains elusive.In this study,we performed transcriptome analysis to compare gene expression profiles at different stages of abdominal fat deposition to identify the key genes and pathways involved in abdominal fat accumulation.We found that abdominal fat weight(AFW)increased gradually from day 35(D35)to 91(D91),and then decreased at day 119(D119).Accordingly,after detecting differentially expressed genes(DEGs)by comparing gene expression profiles at D35 vs.D63 and D35 vs.D91,and identifying gene modules associated with fat deposition by weighted gene co-expression network analysis(WGCNA),we performed intersection analysis of the detected DEGs and WGCNA gene modules and identified 394 and 435 intersecting genes,respectively.The results of the Gene Ontology(GO)functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes(KEGG)pathway enrichment analyses showed that the steroid hormone biosynthesis and insulin signaling pathways were co-enriched in all intersecting genes,steroid hormones have been shown that regulated insulin signaling pathway,indicating the importance of the steroid hormone biosynthesis pathway in the development of broiler abdominal fat.We then identified 6 hub genes(ACTB,SOX9,RHOBTB2,PDLIM3,NEDD9,and DOCK4)related to abdominal fat deposition.Further analysis also revealed that there were direct interactions between 6 hub genes.SOX9 has been shown to bind to proteins required for steroid hormone receptor binding,and RHOBTB2 indirectly regulates the steroid hormones biosynthesis through cyclin factor,and ultimately affect fat deposition.Our results suggest that the genes RHOBTB2 and SOX9 play an important role in fat deposition in broilers,by regulating steroid hormone synthesis.These findings provide new targets and directions for further studies on the mechanisms of fat deposition in chicken.

A selected population study reveals the biochemical mechanism of intramuscular fat deposition in chicken meat

Background:Increasing intramuscular fat(IMF)is an important strategy to improve meat quality,but the regulation mechanism of IMF deposition needs to be systematically clarified.Results:A total of 520 chickens from a selected line with improved IMF content and a control line were used to investigate the biochemical mechanism of IMF deposition in chickens.The results showed that the increased IMF would improve the flavor and tenderness quality of chicken meat.IMF content was mainly determined both by measuring triglyceride(TG)and phospholipid(PLIP)in muscle tissue,but only TG content was found to be decisive for IMF deposition.Furthermore,the increase in major fatty acid(FA)components in IMF is mainly derived from TGs(including C16:0,C16:1,C18:1n9c,and C18:2n6c,etc.),and the inhibition of certain very-long-chain FAs would help to IMF/TG deposition.Conclusions:Our study elucidated the underlying biochemical mechanism of IMF deposition in chicken:Prevalent accumulation of long-chain FAs and inhibitions of medium-chain FAs and very long chain FA would jointly result in the increase of TGs with the FA biosynthesis and cellular uptake ways.Our findings will guide the production of high-quality chicken meat.

The regulation of IMF deposition in pectoralis major of fast-and slow-growing chickens at hatching

Background： The lipid from egg yolk is largely consumed in supplying the energy for embryonic growth until hatching. The remaining lipid in the yolk sac is transported into the hatchling＇s tissues. The gene expression profiles of fast-and slow-growing chickens, Arbor Acres（AA） and Beijing-You（BJY）, were determined to identify global differentially expressed genes and enriched pathways related to lipid metabolism in the pectoralis major at hatching.Results： Between these two breeds, the absolute and weight-specific amounts of total yolk energy（TYE） and intramuscular fat（IMF） content in pectoralis major of fast-growing chickens were significantly higher（P 〈 0.01,P 〈 0.01, P 〈 0.05, respectively） than those of the slow-growing breed. IMF content and u-TYE were significantly related（r = 0.9047, P 〈 0.01）. Microarray analysis revealed that gene transcripts related to lipogenesis, including PPARG, RBP7, LPL, FABP4, THRSP, ACACA, ACSS1, DGAT2, and GK, were significantly more abundant in breast muscle of fast-growing chickens than in slow-growing chickens. Conversely, the abundance of transcripts of genes involved in fatty acid degradation and glycometabolism, including ACAT1, ACOX2, ACOX3, CPT1 A, CPT2, DAK, APOO, FUT9, GCNT1,and B4 GALT3, was significantly lower in fast-growing chickens. The results further indicated that the PPAR signaling pathway was directly involved in fat deposition in pectoralis major, and other upstream pathways（Hedgehog, TGFbeta, and cytokine–cytokine receptor interaction signaling pathways） play roles in its regulation of the expression of related genes.Conclusions： Additional energy from the yolk sac is transported and deposited as IMF in the pectoralis major of chickens at hatching. Genes and pathways related to lipid metabolism（such as PPAR, Hedgehog, TGF-beta, and cytokine–cytokine receptor interaction signaling pathways） promote the deposition of IMF in the pectoralis major of fast-growing chickens compared with those that grow more slowly. These findings provide new insights into the molecular mechanisms underlying lipid metabolism and deposition in hatchling chickens.

Chicken gga-miR-1306-5p targets Tollip and plays an important role in host response against Salmonella enteritidis infection

Background: Increasing evidence indicates that micro RNAs(mi RNAs) are involved in inflammatory response and immune regulation following pathogen invasion. The purpose of this study was to elucidate the roles played by Gallus gallus micro RNA-1306-5 p(gga-mi R-1306-5 p) in host responses against potential invasion by Salmonella enteritidis(SE) in chickens and the underlying mechanisms.Results: In present study, the expression levels of gga-mi R-1306-5 p were determined in both tissues and HD11 cells. The results showed that gga-mi R-1306-5 p was significantly increased following SE infection or lipopolysaccharide(LPS) stimulation. The dual luciferase reporter assay further validated that gga-mi R-1306-5 p targeted the Toll-interacting protein(Tollip), and thereby participated in the regulation of immune response against SE or LPS stimulation through binding with the 3′-untranslated region(3’UTR) of Tollip. Additionally, the expression of Tollip was significantly blocked by over-expressed gga-mi R-1306-5 p. The underlying mechanisms by which ggami R-1306-5 p modulated the production of pro-inflammatory cytokines were also investigated. Molecular biological assays demonstrated that overexpression of gga-mi R-1306-5 p promoted the production of pro-inflammatory mediators, including NF-κB, TNF-α, IL-6, and IL-1β, which produced effects similar to those of Tollip knockdown.Conclusions: Taken together, gga-mi R-1306-5 p induced by SE or LPS, regulates the immune response by inhibiting Tollip, which activates the production of inflammatory cytokines. This study has provided the first direct evidence that gga-mi R-1306-5 p targets Tollip, and is involved in the host response against SE.